What happened when $4.8 million worth of gold bars were stolen from an armored truck on Sunday?

This image comes from the Trans Value website.TransValue Inc.(Reuters) - Robbers who took $4.8 million in gold bars from an armored truck in North Carolina over the weekend most likely knew the vehicle was carrying valuables when they attacked it during an unplanned stop on a remote stretch of highway, authorities said on Wednesday.

"There's a possibility that they could have been doing some type of surveillance" of the tractor-trailer and its route, Wilson County Sheriff Calvin Woodard Jr. said during a news conference in Wilson County, North Carolina.

The armored vehicle from TransValue Inc, a Miami-based company that specializes in transporting valuables to banks, was traveling from Miami to Massachusetts when it was robbed, Woodard said, and it had taken the route along Interstate 95 one other time.

The truck's two armed guards, employed by TransValue, told police on Sunday around 7 p.m. that they had pulled their truck onto the side of the highway when one felt sick from gasoline fumes coming from the truck after they had stopped for food and fuel in South Carolina, Woodard said.

The guards said they got out of the truck without their weapons, he said.

They were immediately accosted by three armed men with Cuban accents who forced them onto the ground, tied their hands with duct tape and zip ties and walked them into the woods, he said.

Woodard said a suspicion that the robbery could be an inside job may be attributed to a language barrier between officers and the Spanish-speaking guards, but it has not been ruled out. The guards, however, have been cooperative, he said.

"Right now, they're still considered victims," he said.

Police found traffic cones that had been placed at the scene and traced them to a Florida business, Woodard said.

The alleged robbers, who were driving a white, late-model cargo van, cut a bar-type lock on the back of the tractor-trailer and offloaded 275 pounds of gold bars from barrels inside it, estimated to be worth $4.8 million, Woodard said.

The lock on the truck was "like something you'd buy at Lowe's," he said.

Authorities described one suspect as a heavyset man around 40 wearing a red traffic vest and said he told the guards he was a police officer. Another was a man wearing a hooded jacket and all-black clothing, Woodard said. The victims could not offer a description of the third suspect.